{"cve":"CVE-2024-49882","nvd":{"published":"2024-10-21T18:15:10.790","modified":"2026-08-04T11:20:55.380","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix double brelse() the buffer of the extents path\n\nIn ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been\nreleased, otherwise it may be released twice. An example of what triggers\nthis is as follows:\n\n  split2    map    split1\n|--------|-------|--------|\n\next4_ext_map_blocks\n ext4_ext_handle_unwritten_extents\n  ext4_split_convert_extents\n   // path->p_depth == 0\n   ext4_split_extent\n     // 1. do split1\n     ext4_split_extent_at\n       |ext4_ext_insert_extent\n       |  ext4_ext_create_new_leaf\n       |    ext4_ext_grow_indepth\n       |      le16_add_cpu(&neh->eh_depth, 1)\n       |    ext4_find_extent\n       |      // return -ENOMEM\n       |// get error and try zeroout\n       |path = ext4_find_extent\n       |  path->p_depth = 1\n       |ext4_ext_try_to_merge\n       |  ext4_ext_try_to_merge_up\n       |    path->p_depth = 0\n       |    brelse(path[1].p_bh)  ---> not set to NULL here\n       |// zeroout success\n     // 2. update path\n     ext4_find_extent\n     // 3. do split2\n     ext4_split_extent_at\n       ext4_ext_insert_extent\n         ext4_ext_create_new_leaf\n           ext4_ext_grow_indepth\n             le16_add_cpu(&neh->eh_depth, 1)\n           ext4_find_extent\n             path[0].p_bh = NULL;\n             path->p_depth = 1\n             read_extent_tree_block  ---> return err\n             // path[1].p_bh is still the old value\n             ext4_free_ext_path\n               ext4_ext_drop_refs\n                 // path->p_depth == 1\n                 brelse(path[1].p_bh)  ---> brelse a buffer twice\n\nFinally got the following WARRNING when removing the buffer from lru:\n\n============================================\nVFS: brelse: Trying to free free buffer\nWARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90\nCPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716\nRIP: 0010:__brelse+0x58/0x90\nCall Trace:\n <TASK>\n __find_get_block+0x6e7/0x810\n bdev_getblk+0x2b/0x480\n __ext4_get_inode_loc+0x48a/0x1240\n ext4_get_inode_loc+0xb2/0x150\n ext4_reserve_inode_write+0xb7/0x230\n __ext4_mark_inode_dirty+0x144/0x6a0\n ext4_ext_insert_extent+0x9c8/0x3230\n ext4_ext_map_blocks+0xf45/0x2dc0\n ext4_map_blocks+0x724/0x1700\n ext4_do_writepages+0x12d6/0x2a70\n[...]\n============================================","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-415"],"references":["https://git.kernel.org/stable/c/230ee0535d01478bad9a3037292043f39b9be10b","https://git.kernel.org/stable/c/32bbb59e3f18facd7201bef110010bf35819b8c3","https://git.kernel.org/stable/c/68a69cf60660c73990c1875f94a5551600b04775","https://git.kernel.org/stable/c/7633407ca4ab8be2916ab214eb44ccebc6a50e1a","https://git.kernel.org/stable/c/78bbc3d15b6f443acb26e94418c445bac940d414"],"products":["debian:debian_linux","linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:56:33.105311382+00:00"},"epss":{"cve":"CVE-2024-49882","score":0.00319,"percentile":0.24936,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}